Uploading your own is simple.
Find a pic you like (mine is one Mr K took at the Peaks Meet) and save it somewhere on your PC. Then check its size, and if you need to resize it to no more than 105 pixels.
Scroll down your Profile and click on upload your own. Find it. Click load. Bingo!
Otherwise, go onto Google or whatever and search for Free Avatar Images. Pick one you like and save/copy the url code. Then, back into your profile and load it. Done.